Animal BT Studying Notes (2) PDF

Why is Drosophila used as a model for biotechnology research? 1) Small & extremely easy to handle 2) Sexual Dimorphism (males & females are different) 3) Non-pathogenic 4) Short-generation lifetime 5) Can be cultured at a low cost in a limited space 6) Fully sequenced genome coupled with...

Why is Drosophila used as a model for biotechnology research? 1) Small & extremely easy to handle 2) Sexual Dimorphism (males & females are different) 3) Non-pathogenic 4) Short-generation lifetime 5) Can be cultured at a low cost in a limited space 6) Fully sequenced genome coupled with molecular, genetic, and bioinformatics tools enhance the translational utility How do we distinguish between male & female Drosophila? Male Female Presence of distinct black patch at the Absence of distinct black patch at the abdomen abdomen Presence of sex combs, a row of dark bristles Absence of sex combs on the tarsus of the first leg Presence of cluster of spiky hairy - Claspers; Absence of calspers surrounds the anus and genitals, used to attach to female What is the general life cycle of Drosophila? Drosophila development is holometabolous: Fertilized eggs → Larva → Pupa → Adult What are the general steps of Drosophila Development? 1) Embryogenesis 2) Pattern Formation  3) Homeotic genes What are the steps of the embryogenesis stage of Drosophila? 1) Fertilization - triggers mitosis in the embryo 2) Several nuclear divisions without cytokinesis occur in the early embryo. At the 10th division, nuclei migrate towards the surface of embryo, resulting in the formation of syncytial blastoderm. 3) At the 13th division, the membrane invaginates and encloses the nuclei, leading to cellularization and the formation of the cellular blastoderm. At the time of cellularization, major body axes & segment boundaries are determined. 4) After cellularization, the embryo proceeds through gastrulation: cells from the ventral surface invaginate to create ventral furrow (critical for the formation of mesoderm) 5) At the anterior and posterior ends of the ventral furrow, prospective endoderm invaginates during gastrulation. Following this, ectodermal cells converge with the mesoderm and migrate to the ventral midline, forming the germ band that will develop into the embryo's trunk. 6) The germ band extends posteriorly and wraps around the dorsal surface of the embryo. At this extended state, several morphogenetic processes occur, including organogenesis, segmentation, & segregation. What are the general steps of the Pattern Formation Stage in Drosophila? Metamorphosis of a simple egg into an adult with a complex body plan requires three classes of genes: 1) Maternal genes - embryonic patterning; bicoid, nanos 2) Segmentation genes - gap, pair-rule, hunchback and segment polarity genes 3) Homeotic genes - Segments achieve unique identities through this genes Explain the roles of Maternal genes. - Bicoid mRNA - head development; triggers expression of hunchback gene - Nanos mRNA - tail development; inhibits expression of hunchback gene Explain the roles of Segmentation genes. - Hunchback gene - regulates gap gene expression; specifies anterior structures in a concentration-dependent (head & thorax) - Gap genes - triggers gap rule - Pair-rule genes - trigger segment polarity; express stripes of the embryo - Segment polarity genes - defines the antero-posterior axis What are the Homeotic Genes in Drosophila? - Homeosis - represents the transformation of one structure of the body into the homologous structure of another body segment - Homeotic genes consists of 180 nucleotides consensus sequences - homeobox - Mutations in these genes result in development of the elements of the specified pattern with inappropriate identities Provide an example of Homeotic genes. - Antennapedia (ANTP) - dominant mutation in this gene transforms the antennal structures on the head into an additional second leg How do we know so much about homeotic genes? - Due to pioneering works on bi-thorax complex (BX-C) - Hox genes have also been found and studied in many other organisms ranging from invertebrates to vertebrates, including mammals What is the order of the genes involved in ? - HOX-genes on the chromosome is the same as the order of the segments that they affect along the anterio-posterior axis Provide some examples of applications of D. melanogaster in drug discovery? 1) Neurodegenerative Diseases 2) Metabolic Disorders and Diabetes 3) Cancer 4) Cardiovascular 5) Inflammation & Infectious Diseases